1. Field of the Invention
The present invention relates to an ink set for inkjet recording and an image forming method.
2. Description of Related Art
A recording method utilizing an inkjet method is widely used since a high quality image can be recorded on a wide variety of recording media by, for example, ejecting ink droplets from multiple nozzle holes arranged on an inkjet head.
Components contained in an ink includes a colorant, and pigments are widely used as the colorant. Pigment inks become more viscous as solvent components contained in the inks evaporate, and gradually solidify. The pigment inks that have solidified hardly redissolve thereafter. Therefore, progression of thickening and solidification of a pigment ink causes gradual deposition of the pigment ink at, for example, a nozzle tip of an inkjet head, and resultantly causes narrowing and/or clogging of nozzle holes, and eventually causes failures such as a deviation of the direction in which the ink is ejected and inability to eject the ink. The progression of the adhesion and deposition of the pigment ink makes it difficult to maintain the ejection quality by using a nozzle cap, a wiping unit, or the like, thereby deteriorating image forming properties as time passes.
In view of this circumstance, a variety of studies concerning cleaning liquids (so-called maintenance liquids) used for cleaning or wiping of an inkjet recording head (so-called ejection head) or the like to which a pigment ink has attached are being conducted. A specific example of cleaning liquids known in the art is a cleaning liquid for an inkjet printer head disclosed in, for example, Japanese Patent No. 4,087,822. This cleaning liquid is intended to wash a non-aqueous photosensitive ink including a specific polymerizable compound, a photopolymerization initiator, and a pigment, and a difference in solubility parameter (SP value) between the cleaning liquid and the photosensitive ink is ±2(MPa1/2). Further, a maintenance liquid for removing a pigment-containing aqueous ink is known (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2011-68085) which has a pH of from 6.0 to 8.5 and which includes at least water, a water-soluble organic solvent having an SP value of 27.5 MPa1/2 or lower, a basic compound, and an acidic compound.